“We know that if we play really good defense and get the ball back to our offense, it’ll be a good day for us. That’s the game plan.”

Kelly tries to hurry defenses into mistakes and mismatches. He usually wants to snap the ball within 15 seconds of a play’s end. NFL substitution rules require the defense get time to swap out players if the offense is substituting during the same dead-ball period, except with less than two minutes remaining in a half. But if the offense does not substitute, it can go as fast as possible without having to wait on the defense to sub.

What Kelly’s hurry-up offense has done to many teams is catch them having to keep 11 defenders on the field from the previous play(s) that don’t match up well with the offensive guys Kelly has employed — say, a base defense with four cover men against three- or four-wide receiver sets. Kelly’s teams have also worn out defenses with their pace, forcing tired starters out of the game and far-less-talented reserves in to defend key downs.

Criticism that Kelly’s go-go ways at Oregon wouldn’t fly in the NFL vanished quickly in his debut season of 2013. Kelly’s Eagles put up 400- and 500-yard games as he turned what had been a 4-12 team the previous season into a 10-6 one that made the NFC playoffs.

But on Dec. 7, 2014, the Seahawks’ defense throttled the Eagles in Philadelphia.

Kelly’s offense sometimes rushed players onto the field like line changes in hockey. Other times, Kelly kept all 11 of his players on the field and the Eagles snapped the ball within a dozen seconds.

The Seahawks started that game in nickel defense, five defensive backs, and stayed in that.

“Whatever we have out there,” Wright said. “We can keep out there, because our guys can play (multiple roles).

“We can play the same defense and so we won’t have to sub guys in and out, even if they’re subbing guys in and out. We can handle that really good.”

With interchangeable defenders — Earl Thomas and Kam Chancellor melding free- and strong-safety responsibilities, linebackers for every down rather than situational ones — all 11 of Seattle’s defenders stood watching Kelly’s Eagles run around frantically between plays. All-Pro middle linebacker Bobby Wagner sometimes gave only simple looks to quickly relay the defensive calls. And Seattle pounced.

It led to a 24-14 Seahawks victory, but it wasn’t that close. The Seahawks held those Eagles to 139 total yards. It remains the least-productive day by an NFL offense coached by Kelly.

You’d likely need to go back before Kelly was calling Oregon’s offense and averaging 489 yards per game there, and before he was the coordinator at lower-division New Hampshire, his alma mater in his home state, starting in 1999 to find his offense so throttled.

His speedy Eagles were two for 11 on third downs against the Seahawks. They had just 18 minutes of possession time and 45 plays in the lopsided 60 minutes. All that no huddling and rushing to create mismatches created short drives and a tired Philadelphia defense instead.

This past week, Kelly hit on why Seattle’s defense feels it is perfectly suited to defend his hurry-up attack.

“They’ve been around each other for a long time,” he said. “I think they really understand how each other works on the defensive side of the ball.”

That’s exactly how the Seahawks plan to do it against his 49ers Sunday.

Defense is what Seattle is going to likely lean on to bounce back from last weekend’s 9-3 loss at Los Angeles. Quarterback Russell Wilson is still playing on a sprained ankle. Lead running back Thomas Rawls is doubtful to play with a bruised shin. Seattle’s new offensive line has gotten pushed around in the first two games.

Whatever, says the Seahawks’ defense. It is ranked No. 1 in the league again early this season.

And it believes that against Kelly, versatility means victory.

“So it really didn’t work in Philly. That’s why,” Wagner said of Kelly’s offense. “I think we are so versatile in our personnel that it wasn’t really going to work out, because we weren’t having guys run in and out. We were staying true.

“It is huge. That’s their big thing. They try to get us stuck in a base defense versus a nickel team, or what have you. But everyone (on our defense) is able to do everything.

The Seahawks’ defense enter Sunday allowing 248.5 yards per game. So far this season they’ve been continuing as the No. 1 scoring defense they’ve been in each of the past four seasons. Seattle has surrendered just 19 points in the first two games.

Now come the 49ers. Quarterback Blaine Gabbert is the NFC’s third-lowest rated passer (ahead of Los Angeles’ Case Keenum and Tampa Bay’s Jameis Winston). Gabbert’s completion rate is 54 percent so far this season. Kelly spent part of this week having to answer whether he was considering a change to former starter Colin Kaepernick.

San Francisco’s Carlos Hyde has yet to become the consistently stellar running back the Niners drafted him to be out of Ohio State. Hyde has 122 rushing yards through two games; he had 34 yards on 14 carries last week in San Francisco’s 46-27 loss at Carolina.

Nine of the 11 Seahawks who will start on defense Sunday played in that game against Kelly in Philadelphia in 2014. That includes the outside linebackers that will start on each side of Wagner, Wright and Mike Morgan, plus three of the four defensive backs behind him — Richard Sherman, Thomas and Chancellor — and ends Michael Bennett and Cliff Avril.

That core has been together since the Super Bowl-winning season of 2013.

Wagner often doesn’t even need to take the time between plays to make verbal calls. Or even hand-signaled ones.

“Oh, it’s super easy. I look over at K.J. I look over at Kam, I look behind me to Earl, and they already know what I’m thinking,” Wagner said. “I’ve already got a rhythm with how I get them the call. It’s just pretty much a thumbs up, or a nod or a look like, ‘OK, you got it.’ A lot of it doesn’t have to be verbal.”

Wagner said it’s been that way since 2014, when the Seahawks broke Kelly’s fast-break offense.

That gives Seattle’s defense supreme confidence.

“I believe we’re really good at it, especially with right hand signals and the simplicity of our defense,” Wright said. “We can just get a call in there, line up really fast and know what’s coming.

“I don’t believe it will be too much of a hassle on our hands. But it’s something we have to practice and get ready for.”

HAWKS SIGN MAGEE

Due to the injuries to Rawls and C.J. Prosise, Seattle signed second-year free-agent running back Terrence Magee off its practice squad to the open spot it had on the 53-man active roster.

The 5-foot-9, 215-pound Magee was an undrafted rookie last season for Baltimore, out of LSU.

Seahawks gameday

SAN FRANCISCO 49ERS (1-1) AT

SEATTLE SEAHAWKS (1-1)

Sunday 1:05 p.m., CenturyLink Field

TV: Ch. 13 Radio: 710-AM, 97.3-FM.

The series: The Seahawks have won the past five meetings — including the NFC Championship Game in January 2015, in Seattle — and have won seven of the past eight games against the 49ers dating to the end of the 2012 season. Seattle leads the all-time series in regular season, 19-15. The 49ers last won in Seattle on Dec. 24, 2011, 19-17, during the only non-playoff season Pete Carroll has had as the Seahawks’ coach.

SEATTLE’S KEYS

Do it with ‘D’: Quarterback Russell Wilson is still playing on a sprained ankle. Lead running back Thomas Rawls is iffy, at best, to play with a bruised shin. The offensive line remains unsettled and in need of improvement, to say the least. Time for another game won by the league’s top-ranked defense. It absolutely shut down coach Chip Kelly’s fast, no-huddle offense the only other time the Seahawks played it, two years ago at Philadelphia. Seattle’s defense has allowed just 19 points through two games this season. Problem is, the offense has only scored only 15.

Have Clark on a short leash: Kelly’s fast pace largely limits defense’s abilities to substitute. That played into Seattle’s defensive strengths of versatility the last time the Seahawks faced him. But one of Seattle’s best weapons early this season has been Frank Clark entering on third downs for speed rushes inside against slower, overmatched guards and centers. To get Clark even on the field Sunday to disrupt some more, he needs to be constantly at his defensive coaches’ sides — and as fast getting off the sidelines into the game as he’s been getting off the ball at the snap.

Give Michael the ball: He’s averaging 5 yards per rush this season. He averaged 6 per carry last week in L.A. So why did Christine Michael get just 10 carries against the Rams — especially with Rawls out hurting? If the coaches trust Michael in this second Seattle stint as they say they do, if they are re-committing to the running game this week as they’ve said they are, No. 32 should break his career high of 17 carries, particularly against San Francisco’s defense that is allowing 120.5 yards rushing per game.

The pick: Seahawks, 17-6.

PRIME NUMBERS

SEATTLE

32 — Christine Michael, RB (5-10, 221, fourth season): Rawls is banged up. Wilson’s ankle is still sprained. Time to see if Michael can be “The Man.”